The present invention relates, in general, to point-of-use distillation systems, and more particularly to compact, continuous-flow distillers for the purification of drinking water.
The global need for safe drinking water is commonly recognized, for the health problems resulting from chemicals, bacteria and viruses in drinking water has been well documented. Many products, including water distillation devices, have been developed in attempts to provide safe water for drinking, but problems still exist. For example, reverse osmosis (RO) point of use water purification systems have limited and unsustainable contaminant removal, can allow the formation of biofilm on filter membranes, and produce waste water. Research has shown that biofilming can be reduced by timely and critical maintenance, but it cannot be completely eliminated and backflushing may contaminate the system. Ultraviolet (UV) water purification systems only address the problem of microbial contamination, and do not remove other contaminants from water. Furthermore, changing turbidity conditions in the water reduces the ability of such systems to kill microbes. Distillation is the oldest and most reliable technology for point of use water purification, for it is reliable, sustainable, and removes a greater percentage of contaminants from water than any other technology. However, difficulties have been encountered in the development of acceptable point of use distillers, and these problems have prevented their widespread use.
A common problem in prior art distillers is the difficulty involved in properly cleaning the boiler, for it usually is difficult to get to the boiler and difficult to clean scale from its interior. The buildup of scale in the boiler tanks of distillers is partially due to the fact that untreated influent water contains bicarbonate ions which will initially break down into carbonate ions, causing the formation of scale. This problem can be reduced by preconditioning or softening the influent water and by preheating influent water prior to entering the boiler. Partial, instead of complete, draining of the boiler can also reduce scale buildup, but periodic cleaning is still required and the construction of most prior distillers have made the cleaning process so complicated that the distiller gradually becomes less efficient.
Although numerous attempts have been made to facilitate the descaling and cleaning of distillers, the problem has not been completely solved, for most such attempts have resulted in additional plumbing requirements or additional components, which increase the cost of purchasing and maintaining the units. For example, some distillers have water cooled condensers which produce waste water and some have periodic automatic draining of the boiler, but these still do not reduce scale buildup or eliminate the difficulties of cleaning.
Proper cleaning of a typical vapor generating distiller apparatus requires substantial time, labor and prolonged periods of operational downtime. In some cases, cleaning may include introduction of cleaning agents into the apparatus and leaving these agents in place for a period of time. Not only does this require long periods of downtime, but it may also be an unwanted source of pollution and contamination of the distilling apparatus.
Increasingly, another concern about the use of distilling devices is their poor energy efficiency. In order to provide an energy efficient point-of-use distiller which can also produce a continuous flow of distilled water, it is necessary to maintain a steady liquid level in the distiller boiler. However, level sensors and controls generally have been located in the boiler, making it difficult to maintain the needed steady liquid level and, in addition, making it even more difficult to clean the boiler. Further, the introduction of cold water into a boiler interrupts vapor production and reduces energy efficiency.
Yet another concern of distilling devices is the evacuation of volatile organic compounds and chemicals (VOC""s) that are released during the distillation process. These VOC""s, if released in the boiler, can decontaminate the distillate. Other problems in the prior art include the fact that some water purification systems produce too much heat, and electric cooling fans tend to be too noisy.
Of great concern today are anticipated government regulations concerning the sanitation of point of use (POU) devices. Sanitation regulation will bring added expense and potential liability to the POU industry. Adding UV upstream and downstream of a reverse osmosis device will not completely eliminate biofilming of RO membranes nor will it match the contaminant removal of distillation. Distillation devices are the least likely to become contaminated; however, sanitation issues still must be properly addressed by facilitating the sanitizing of a distilled water storage reservoir should it become necessary.
Thus, there is a need for a continuous flow water distillation system which is fast and easy to clean and maintain, is energy efficient, incorporates thermal energy recovery, substantially reduces ambient heat, is less noisy, is easy to sanitize, is simple to construct and which is capable of efficient, reliable, and sustainable operation over a long period of time.
It is, therefore, an object of the invention to provide a simple, energy efficient and easy-to-maintain, continuous flow, point of use distiller for providing clean, pure drinking water.
Another object of the invention is to provide a point of use, continuous flow water distiller utilizing a boiler having a removable vessel consisting of inner and outer containers for vapor generation, which reduces the time, labor and operational downtime normally associated with proper cleaning of such apparatus.
Another object of the invention is to provide a drinking water distiller wherein the initial cost associated with the device is amortized by savings in reduced time, labor and operational downtime.
Another object of the invention is to provide a drinking water distiller which utilizes a simplified system for detecting, controlling and maintaining liquid level in a removable vapor generating vessel which is provided in the distillation system.
A further object of the invention is to provide a liquid level measuring device for a distiller which is noninvasive and which is capable of being utilized in a wide variety of other applications and in combination with a variety of containers without requiring substantial modification of the containers.
Another object of the invention is to provide a preheating chamber for a point-of-use distiller which substantially increases energy efficiency by eliminating influent interruption of vapor production and which releases and evacuates VOC""s from influent water prior to entering the boiler.
Another object of the invention is to provide a heat exchanger for thermal energy recovery to further increase energy efficiency and to substantially reduce heat released to the ambient.
Another object of the invention is to reduce cooling fan noise by incorporating aerodynamics.
Yet another object of the invention is to provide a device which is easy and inexpensive to sanitize should that become necessary.
Briefly, the present invention is directed to a continuous flow drinking water distiller which utilizes stacked, vertically-arranged components to provide a compact and energy efficient distillation device which may be quickly and easily serviced, maintained and sanitized. The device includes a housing which contains a double-walled vessel which serves as the boiler for the distiller and to which water is supplied from an external source through suitable filters. A heating source is provided to boil water in the double-walled vessel, producing steam which is supplied to a condenser, with the condensate being directed to a storage container located below the boiler. A noninvasive liquid level sensor maintains the water level in the boiler and a controller is provided to activate the boiler when water is required for the storage reservoir. Located between the reservoir and the boiler in the vertical stack of the distiller device is a chiller tank which receives and cools water from the reservoir, as needed.
The device of the present invention is a completely closed system producing pure condensed steam distilled water so that sanitizing is less of a concern than is the case with other technologies. However, if sanitizing of the storage reservoir should become necessary, the device is constructed so that a side panel of the cabinet can be removed and the reservoir easily slid out to be sanitized or replaced with a sanitized reservoir. Alternatively, a steam cleaning tube (not shown) may be provided to connect the vapor port of the boiler to the reservoir whereby the reservoir can be steam cleaned on location. Another alternative is simply to shut the condenser fan off so that steam, instead of distillate, is directed into the reservoir from the boiler.
More particularly, in a preferred form of the invention the boiler vessel includes an inner container nested within a somewhat larger outer container. The inner and outer containers forming the vessel may be stainless steel, for example, with each container having a bottom wall and a generally cylindrical side wall formed with outwardly extending flanges at the top peripheral edge. The outer vessel may have attached legs for supporting and/or mounting the apparatus within the distiller device, for example, although other mounting devices may be provided, while the inner container is supported within, and spaced from, the outer container by its top flange and a suitable gasket which seals the flanges. Water, or other liquid to be heated, is delivered to the double-wailed boiler by way of an inlet port through the side wall of the outer container, preferably below the desired liquid level, with an inlet tube being attached to this port. If desired, a drain port for attaching a drain line may be located on the bottom of the outer container for draining liquid from the boiler. Such a drain port may be connected to a xe2x80x9cTxe2x80x9d fitting through which liquid to be heated can be delivered to the boiler.
A single vessel boiler may be utilized as an alternative to the preferred inner and outer vessel boiler, in which case the vessel is removably seated within an open top insulative boiler housing or pocket. A drain pipe is attached to a drain port in the bottom wall of the vessel and protrudes vertically downwardly through an orifice in the bottom wall of the housing or pocket. A drain tube is removably connectable to the drain pipe by a suitable quick connect. Water to be treated preferably is introduced into the single vessel boiler by way of a supply line which is connected to a nipple or a xe2x80x9cTxe2x80x9d connector attached to the drain line.
In the preferred form of the invention, the side and bottom walls of the inner container and the somewhat larger outer container are spaced apart to provide a preheating chamber for receiving liquid introduced through the inlet port. Small ports may be provided in the upper part of the side wall of the outer vessel, above the water level in the preheating chamber, for venting volatile organic compounds and chemicals released by the preheating process. An orifice in the bottom of the inner container permits liquid to flow from the inlet port through the preheating chamber and into the inner vessel. A heat source is provided for the double-walled vessel and preferably is a heater attached to a boiler lid and extending downwardly into the liquid within the inner container. When the heater is on, heat from the heated liquid in the inner container radiates outwardly into the space between the containers to preheat the liquid in the preheating chamber.
The boiler lid also carries a vapor outlet tube for delivering vapor from within the boiler to a condenser for subsequent delivery of distillate to the storage reservoir.
A heat exchanger may be provided inline between the boiler and the condenser for effecting thermal energy recovery whereby energy efficiency is increased and radiant heat to the ambient is substantially decreased. The heat exchanger is connected to preheat influent liquid before it is supplied to the preheating chamber.
To detect, control, and maintain a desired liquid level in the boiler vessel of the distiller of the present invention, a noninvasive sensor and controller is provided. Although the sensor and controller is described as a part of the distiller of the present invention, it also may be utilized for noninvasively controlling liquid level in any container. In addition, it can be used with varying operating pressures as well as with different liquid temperatures, viscosities, turbidity and specific gravity. Such a sensor is valuable in a distiller since the maintenance of a steady liquid level in the boiler substantially reduces the formation of scale caused by fluctuating liquid levels. A simplified version of the apparatus is useful for simply detecting an empty or low liquid level in an associated container or a bottom-draining container.
The noninvasive sensor and controller of the present invention, hereinafter referred to simply as a sensor, detects, measures and controls liquid level within a container from a location outside the container. In one embodiment, the sensor includes an enclosed container having, for example, a cylindrical side wall with top and bottom closures, or caps. A first tube extends through the bottom cap of the housing and is connected to the drain tube of a container in which the liquid level is to be measured. The top of the sensor housing is vented to atmosphere through a tube in the top sensor cap, and a reed float switch assembly mounted on the top cap protrudes downwardly into the sensor housing. The sensor is located so that the reed switch operates at the desired levels in the container which are to be detected; thus, the sensor may be located to detect the lowermost level in the container or the highest desired level in the container, or two switches may be provided in the sensor housing to measure both.
Another embodiment of the noninvasive sensor includes multiple reed switches for detecting various levels of liquid in the container and for controlling a solenoid valve which regulates the flow of inlet water to the container. The inlet water may flow from the solenoid valve, through the sensor housing, and then to the container to be controlled, or may flow from the solenoid valve to a xe2x80x98Txe2x80x99 connector and from the connector to both the sensor and the container. The xe2x80x98Txe2x80x99 connection is desirable, for example, when a heat exchanger is being utilized in line between the boiler and condenser.
In a further embodiment, the upper portion of the sensor housing may be connected to the upper portion of the container in which the liquid level is to be controlled in order to provide pressure equalization between the sensor and the container. Such a connection is desirable when the container being controlled is operating at pressures other than atmospheric. It will also be understood that the outlet from the solenoid-controlled inlet valve may be connected directly to the liquid container or to a drain line for the container, rather than being connected through the sensor housing. Furthermore, suitable alarms may be provided in connection with the sensor.
The distiller of the present invention may be a stand-alone floor unit, or may be configured as a portable counter-top batch or continuous flow distillation apparatus having a completely open top for quick and easy removal and cleaning of the boiler and a heat source that never has to be cleaned. The distiller may also be configured to have the features described above but adapted for under-counter and under-sink installations in typical kitchens to provide a convenient source of pure water for delivery to sink faucets, refrigerator ice makers or cold water supplies, or for various other applications.